The present invention relates generally to getter pumps and, more particularly, to a getter pump in which a plurality of getter elements are housed in a frame having opposing sidewalls with slots formed therein for receiving the getter elements, a method of forming a getter pump component, and a preformed sheet of metal for use in forming components of a getter pump.
In the field of vacuum technology so-called "getter pumps" have been known for several decades. Getter pumps are static devices, i.e., devices which operate without moving parts. The ability to operate without moving parts provides getter pumps with at least two significant advantages. First, lubrication is not required. This is important in applications related to the semiconductor industry because lubricants can contaminate the chamber to be evacuated. Second, getter pumps do not transmit any undesirable vibrations to the system to which they are connected.
The operation of getter pumps is based on the chemisorption of all gases, except for noble gases, by nonevaporable getter materials, which are sometimes referred to as "NEG materials." The primary NEG materials are alloys based on zirconium and titanium which may include elements such as aluminum, vanadium, iron, nickel, or other transitional elements, or combinations thereof. Commercially available NEG materials produced by SAES Getters S.p.A. of Milan, Italy, the assignee of the present application, include the alloys sold under the trade names St 101.RTM. and St 707.TM.. The St 101.RTM. alloy has a composition of 84 wt % Zr and 16 wt % Al. The St 707.TM. alloy has a composition of 70 wt % Zr, 24.6 wt % V, and 5.4 wt % Fe.
The active members of getter pumps are referred to as "getter elements." One known method for forming getter elements involves adhering, e.g., by lamination, NEG material in powder form to a suitable metal support. Getter pumps including getter elements formed in accordance with this method are disclosed in U.S. Pat. No. 4,137,012 to della Porta et al., which is assigned to SAES Getters S.p.A., and Japanese Laid-Open Patent Application (Kokai) No. 4-5480. More recent getter pumps have included getter elements formed by sintering NEG material powders as disclosed, for example, in U.S. Pat. No. 5,320,496 to Manini et al. and U.S. Pat. No. 5,324,172 to Manini et al., both of which are assigned to SAES Getters S.p.A.
Regardless of the manner in which the getter elements are formed, it is necessary to keep the getter material at temperatures of at least 400.degree. C. during operation to ensure optimal performance of the getter material. Furthermore, NEG material requires a starting "activation" treatment at temperatures of at least 400.degree. C. and up to 900.degree. C. over 10-30 minute periods.
Getter elements may be disposed within a getter pump in a variety of ways, e.g., by filling the getter pump with sintered pills obtained from NEG material powders. In known getter pumps the getter elements are preferably mounted on a support having a heating member mounted thereon or nearby to heat the getter elements to the above-mentioned temperatures. Although different types of heating members may be used, infrared lamps are especially advantageous because they are easy to replace, which is important because the life of the heating element is short relative to that of the getter elements. The getter elements also may be regenerated and replaced and, therefore, the getter pump must be easy to disassemble and to reassemble.
In known getter pumps NEG material disks or plates are arranged within the pump with an optimized geometry. In fact, the performance of a getter pump, and in particular its gas sorption rate, depends upon the geometrical relationship between the getter elements. For example, in the case of parallel getter elements, there is an optimum range of spacing with which a maximum gas sorption rate is obtained. At a spacing above or below the optimum spacing, the gas sorption rate decreases. The gas sorption rate further depends upon the effectiveness of the heating member in heating the getter elements, which in turn depends upon geometrical factors. The spacing tolerance in the geometry of a getter pump is therefore a primary factor affecting the performance of the pump. To obtain the desired geometry of the getter elements, metal bearings fastened to the inner walls of the pump body are arranged within a getter pump. This complicates the pump manufacturing process because it requires the use of mechanical assemblies (with screws, etc.) or welding a plurality of metal members. As a result, the tolerances of the geometry of the getter elements provided for in the pump design may be lost during the mechanical assembly stage of the manufacturing process. Further, even when the pumps are manufactured to precise tolerances, problems with tolerances may arise during the life of the pump because of adjustments which occur when the pumps are thermally cycled from room temperature to their operating temperature, which is generally at least 400.degree. C. Tolerance problems also may occur during moving or transporting of the pumps.
In view of the foregoing, there is a need for a getter pump which includes a supporting framework which enables the getter elements to be assembled thereon precisely in a quick and safe operation.